The most obvious answer to this question would be: because we want to. But that’s not the answer I’m looking for, if only for the simple fact that I do not wish to get into a debate on free will right now. What I’m wondering about is: what’s the purpose of kissing? And, to clarify even further: I mean romantic kissing. First time I wondered about this was about a quarter of a century ago, which may have been a sign that my personality is more that of theorist than that of practitioner. I saw a typical B movie on television about an american explorer in a jungle somewhere who fell in love with and kissed an indigenous girl. She responded by saying something like:”Our lips were given to us to feed, why did you use yours to touch mine?” Good question miss!
Kissing and Freud
The most familiar possible explanation for kissing comes from Sigmund Freud. For Freud, kissing was a subconscious return to suckling at the mother’s breast. Take that for romance. I guess that, to many, that explanation seems plausible. However, If kissing is just substitute for suckling a breast, why do we not just suckle each others breast to show our loving appreciation of one another?
Kissing and culture
We may not even realize this, but kissing is not a universal thing for us humans. Not all human cultures do it. The most familiar example of this is probably the Eskimo nose-rub. But across the world there are (or perhaps I should write: were) many cultures that did not kiss untill it was introduced by Western, European, adventurers. African and Asian peoples found the activity disgusting. Swapping saliva? Yuck!
Kissing and biology
But perhaps that swapping of saliva is actually the point. There are other species on our planet that engage in kiss-like behaviour, but -perhaps with the exception of Bonobo apes– this is mostly a bit of nuzzling or giving each other a peck on the cheek. Perhaps the jungle girl sets us on the right track by stating that we have lips (mouths) to feed. Several animal species, birds and insects, bring their potential mate food (often pre-chewed) as a way of courtship. But this behaviour is found mainly in males, not females.
Kissing and genetics
Back to the saliva swapping. Our saliva is full of chemical that provide all sorts of information about our genetic make-up. And studies have shown that when choosing a mate, us humans tend to select someone who has complementary immune-system genes (MHC genes) to ours. This makes sense, since your offspring would have the benefit of a much wider defense against, for example, disease. If you have ever read about these MHC genes you might also know that these genes also largely influence your smell. So why not just sniff each other out like the Eskimos (or Maoris)? Research by Sheril Kirshenbaum (author of ‘The science of kissing: what our lips are telling us’) shows that women can determine by smell alone whether a mann is a potentially good mate as far as genes are concerned (whether he would also be a good father to their offpsring is an entirely different story).
What’s important to know, is that the nose-rub is not a gentle touch of the tips of noses. Eskimos move in real close and personal until their noses are next to each other and then breath in deeply. What they actually do is breathe in each other’s smell. The nose rub does appear to have the same purpose as a kiss, but the way to do it correctly is not more efficient. So the nose-rub and the kiss actually have quite a lot in common. But the kiss has at least one advantage: in their saliva, males transmit testosterone which make a female more responsive.
Whatever mating strategy you choose, you need to get in close and invest a little time. And isn’t that what romance is about anyway?
If you think this post was interesting, you might also like to read this one: Why do we wave?